Developers building with AI agents face a recurring decision: when your agent needs capabilities beyond code — web search, image generation, video, storage — how do you add them?
Three approaches dominate the conversation: MCP servers, Skills, and capability runtimes. They're often positioned as competitors. They're not. They solve different problems at different layers of the stack.
Here's how to choose.
The Three Layers, Defined
MCP Servers: The Transport Layer
MCP (Model Context Protocol) is an open standard for how AI agents connect to external tools. An MCP server is a lightweight program that exposes a set of tools — search, database queries, file operations — that any MCP-compatible agent can call.
MCP solves the connection problem: how does an agent discover and invoke external tools? It standardizes the interface. Instead of every tool having its own protocol, they all speak MCP.
Skills: The Instruction Layer
Skills (also called agent skills or SKILL.md files) are markdown documents that teach an agent how to use a tool or perform a task. A Skill says: "here's how to install the CLI, here's the available commands, here's what to do when you get an error."
Skills solve the instruction problem: how does an agent know what to do with a tool once it's connected? Without a Skill, the agent sees a tool but doesn't understand the workflow.
Capability Runtimes: The Bundling Layer
A capability runtime is a single CLI (or API) that bundles multiple capabilities — image generation, video, web search, cloud storage, publishing — behind one endpoint. Instead of configuring five separate MCP servers, you install one tool.
Capability runtimes solve the consolidation problem: how do you give your agent many capabilities without drowning in configuration, credentials, and token overhead?
The Layer Diagram
┌─────────────────────────────────────────────┐
│ Your AI Agent │
│ (Claude Code, Cursor, Codex, Windsurf) │
├─────────────────────────────────────────────┤
│ │
│ ┌─────────┐ ┌─────────┐ ┌─────────────┐ │
│ │ MCP │ │ Skills │ │ Capability │ │
│ │ Servers │ │ (SKILL) │ │ Runtime │ │
│ │ │ │ │ │ │ │
│ │ Connect │ │ Instruct│ │ Bundle │ │
│ │ tools │ │ agent │ │ capabilities │ │
│ └─────────┘ └─────────┘ └─────────────┘ │
│ │
│ Transport Instruction Consolidation │
│ Layer Layer Layer │
└─────────────────────────────────────────────┘
None of these layers replaces the others. In fact, they work best together:
- MCP connects your agent to a capability runtime
- Skills teach your agent how to use the runtime's commands
- The runtime bundles the capabilities so there's only one thing to connect and instruct
When to Use Each
Use MCP Servers Alone When:
You need one or two specific tools that have well-maintained MCP servers. For example, connecting your agent to your company's internal database via a custom MCP server. Or adding GitHub integration through an existing MCP server.
MCP alone makes sense when:
- You need exactly 1-2 capabilities
- The capabilities are specialized (your database, your API, your Jira)
- You have DevOps support to maintain the server configurations
- Token overhead from 1-2 servers is negligible
Use Skills When:
You want your agent to understand a workflow, not just access a tool. A Skill doesn't just list commands — it teaches the agent the sequence: install, authenticate, configure, verify, use.
Skills are essential when:
- The tool has a multi-step setup process
- Error handling matters ("if you get X error, try Y")
- You want the agent to be self-sufficient with the tool
- You're sharing the workflow across a team
Use a Capability Runtime When:
You need 4+ capabilities and the configuration overhead is becoming unmanageable. This is the most common scenario for individual developers and small teams.
A capability runtime makes sense when:
- Your agent needs image, video, search, storage, and publishing
- You don't want to manage 6 API keys and 5 MCP server configs
- Token overhead from multiple servers is impacting agent performance
- You want one install, one credential, one output format
The Hybrid Approach (What Most Teams Actually Use)
In practice, the best setup is usually a hybrid:
MCP Servers (specialized tools) + Capability Runtime (common capabilities) + Skills (workflow instructions)
Your agent connects to:
- 1-2 MCP servers for internal or specialized tools (database, Slack, Jira)
- 1 capability runtime for common capabilities (image, video, search, storage, publish)
- 1 Skill file that teaches the agent how to use the runtime
This gives you best-of-breed for unique needs and minimal overhead for everything else.
The Token Reality
The hybrid approach isn't just conceptually cleaner — it has measurable impact. Every MCP server adds tool descriptions to your agent's context. With 5 MCP servers, you're burning 15,000-40,000 tokens on tool descriptions.
A hybrid setup with 2 MCP servers + 1 capability runtime drops that to roughly 8,000-14,000 tokens. That's 10-15% more context freed for actual work.
Common Mistakes
Mistake 1: Thinking MCP is Enough
MCP connects tools. It doesn't bundle them, manage their credentials, or reduce their token overhead. If you're running 5+ MCP servers, your agent is paying a tax on every one.
Mistake 2: Thinking Skills Replace Tools
Skills teach workflows. They don't provide capabilities. A Skill can tell your agent how to generate images — but the agent still needs an actual image generation tool behind it.
Mistake 3: Thinking Runtimes Replace MCP
Capability runtimes consolidate common capabilities. They don't replace the need for specialized integrations. Your agent still needs MCP to connect to your internal database or Jira. The runtime handles the generic capabilities most agents share.
The Decision in One Table
| You need... | Use... |
|---|---|
| 1-2 specialized tools | MCP servers |
| Your agent to understand a workflow | Skills |
| 4+ common capabilities | Capability runtime |
| All of the above | Hybrid: MCP + Runtime + Skills |
Bottom Line
The MCP vs Skills vs Capability Runtime debate misses the point. These are three layers of the same stack, not three competing approaches.
MCP is the USB-C port. Skills are the instruction manual. The capability runtime is the device that plugs in.
Your agent needs all three. The question isn't which one — it's how much of each.
Last updated: May 2026